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author | Patrick Ohly <patrick.ohly@intel.com> | 2009-02-12 06:03:37 +0100 |
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committer | David S. Miller <davem@davemloft.net> | 2009-02-16 07:43:34 +0100 |
commit | ac45f602ee3d1b6f326f68bc0c2591ceebf05ba4 (patch) | |
tree | c92c86bd0d89b844a3794c0e441aa2fccb36725f /net/compat.c | |
parent | net: new user space API for time stamping of incoming and outgoing packets (diff) | |
download | linux-ac45f602ee3d1b6f326f68bc0c2591ceebf05ba4.tar.xz linux-ac45f602ee3d1b6f326f68bc0c2591ceebf05ba4.zip |
net: infrastructure for hardware time stamping
The additional per-packet information (16 bytes for time stamps, 1
byte for flags) is stored for all packets in the skb_shared_info
struct. This implementation detail is hidden from users of that
information via skb_* accessor functions. A separate struct resp.
union is used for the additional information so that it can be
stored/copied easily outside of skb_shared_info.
Compared to previous implementations (reusing the tstamp field
depending on the context, optional additional structures) this
is the simplest solution. It does not extend sk_buff itself.
TX time stamping is implemented in software if the device driver
doesn't support hardware time stamping.
The new semantic for hardware/software time stamping around
ndo_start_xmit() is based on two assumptions about existing
network device drivers which don't support hardware time
stamping and know nothing about it:
- they leave the new skb_shared_tx unmodified
- the keep the connection to the originating socket in skb->sk
alive, i.e., don't call skb_orphan()
Given that skb_shared_tx is new, the first assumption is safe.
The second is only true for some drivers. As a result, software
TX time stamping currently works with the bnx2 driver, but not
with the unmodified igb driver (the two drivers this patch series
was tested with).
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/compat.c')
0 files changed, 0 insertions, 0 deletions